1. Field of the Invention
The present invention relates to an improvement in a lubricating system for a 4-cycle engine in which a side cover defining a first valve-operating chamber is bonded to one side of a crankcase defining a crank chamber which accommodates a crank portion of a crankshaft; a head cover defining a second valve-operating chamber leading to the first valve-operating chamber is bonded to a head portion of a cylinder block connected to the crankcase; and a valve-operating mechanism is accommodated in a region extending from the first valve-operating chamber to the second valve-operating chamber, and particularly to a dry-sump-type lubricating system of the above structure in which a lubricating oil is prevented from residing in the crank chamber.
2. Description of the Related Art
There is a conventional lubricating system of a dry sump type, in which an oil tank is mounted on one side of a crankcase, and an oil slinger driven to rotate by a crankshaft is disposed in the oil tank, so that an oil mist produced by stirring an oil stored in the oil tank is supplied to a crank chamber and a valve-operating chamber, as disclosed, for example, in Japanese Patent Application Laid-open No. 2002-38916.
In the above-described lubricating system including the oil tank disposed on one side of the crankcase, it is difficult to compactly form the entire engine including the oil tank. In addition, the disposition of the oil slinger for producing the oil mist results in an increase in the number of parts and complication of the structure. Moreover, the shape of the oil tank is limited to a cylindrical shape by the oil slinger, thereby making it further difficult to compactly form the entire engine.